The long-term objective of our research is to gain a more complete understanding of cell division. This multistep process requires exquisite temporal and spatial coordination of a large number of proteins. In our studies, we use cell division mutants that we have generated in the roundworm, Caenorhabditis elegans. C. elegans is ideal for these studies as it is possible to generate and maintain mutants, including conditional mutations, the worms and embryos are transparent, the embryos are large and easy to obtain, and the patterns of cell division are very similar to that seen in other organisms, including vertebrates. In this proposal, we describe our efforts to 1) characterize the phenotypes more fully in two cell division mutants. Procedures to be used include fluorescence microscopy in fixed and living embryos as well as temperature shift experiments to determine when these proteins are needed. 2) Identify the genes that are mutated in these two mutants. We propose to use techniques including genetic mapping, RNAi, transformation rescue, and DNA sequencing. 3) Begin to investigate how these genes fit with other genes with roles in cell division. We will use genetic and molecular epistasis experiments as well as a novel RNAi screen to look for genes that interact. Because cell division is highly conserved, what we can learn from studying this process in C. elegans may be applicable to other organisms including humans. In cancer, cell division is not properly regulated, and defects in DNA segregation and cytokinesis are common. The C. elegans mutants we are studying share these phenotypic characteristics, so we believe we may gain some insight into mechanisms of cell division that may some day help us to better understand what happens when cell division goes awry in cancer cells.